The present invention relates generally to interferometer techniques. More particularly, the invention provides a method and system for using waveguide in an interferometer. Merely by way of example, the invention has been applied to measuring spatial locations, but it would be recognized that the invention has a much broader range of applicability.
Interferometers have been widely used for spatial measurements. The interferometers include homodyne interferometers, such as conventional Michelson interferometer, and heterodyne interferometers. Homodyne interferometers use laser beams at the same frequency, while heterodyne interferometers use laser beams at different frequencies.
Interferometers measure the phase of a continuous signal for as long as the signal remains stable over all portions of a reference path and a measurement path. The major practical problem with high resolution interferometry is that changes of optical path-lengths in the system, including ones that are not intended, are measured. After optical beams are split in the interferometer, movement of optical components, especially mirrors, add or subtract optical path-length from one of the two beams separately, resulting in a signal that is unrelated to the measurement. Therefore, stability of optical components in the separate legs of the interferometer is usually important. See J. D. Trolinger, Ultra High Resolution Interferometry, Proc. SPIE Vol. 2816, pp. 114–123 (1996).
Hence, it is desirable to improve interferometer techniques.